I've got a 17½' Alumaweld Stryker with a Merc 65 Jet. I've used it in the salt a few times, then dipped it in a freshwater lake to flush the salt out.

What I've got happening is little pits in the hull that I'm sure is caused by electrolysis. I've disconnected all the ground wires from the battery and then reconnected them one by one checking for a ground between the hull and positive post. I found that the main ground wire going to the Merc is grounding to the hull. Is it possible to isolate the motor ground from the hull? What kind of options do I have?

Also, how can I add more zinc? I've only got one piece affixed to the lower unit. I saw on another BB about welding directly to the hull. Is that the most recommended method? Is there a formula, or rule of thumb, for the amount of zinc one should have?

Thanks.

Goharley

Not sure if this may be related but I remember a few threads this winter that mentioned if you did not wash your boat down every time after tailoring it the road deicer would pit aluminum. Just a thought.

I'll bet it's corrosion and not electrolysis. Hose it off with Salt Away. Use that garden type hose dispenser they sell.

HUH?????? Sorry to inform you, but electolysis IS corrosion bud......

Harley, if the only zinc you have is on the motor, that is definetely a (maybe THE) problem. You should have at least one on the hull. You can buy different sizes, bigger the better, that bolt on. I do not think they even make one that "welds" on, since zinc and aluminum would not be compatable for welding.
Get a handle on it now, especially if you are going to do more salt fishing, as once the corrosion (electolysis) starts it can take off really fast..... Get that electrode on your hull man!

MC

MC, how do I know which size to put on? Is there a rule of thumb or formula depending on boat size?

Thanks.

Just keep in mind that you cannot hurt anything by going big..... No overkill in this department (except may looks).
I had two 2"X4" on my 25' Sled and a 1" X 3" on the bottom of my nozzle..... Never had even the slightest pimple or blemish from the salt, but did go through 2 sets of the zinc electrodes.....
Grounding to the hull is a necessary evil, and as long as you have the zinc in place there is no problem. It is the salt and aluminum that together make the electolysis occur. Since Zinc is a an end conductor, if in place it will isolate the electolysis and take the damage (by giving up electrons), thereby saving your hull...... Keep the one on your lower unit in good shape too though...

Good luck!

MC

A couple of things I've done with my sled since I am using it in the salt more than I have anticipated.
1) Zincs - I've got 5. ( go ahead call me paranoid ,I am ) 2 on the hull, 2 on the pump and 1 on the kicker. Remember to brush them occasionally with a stainless steel brush.
2) Run in fresh water after you are done. I dump mine in Lake Samm and run on the trailer for a few minutes. Run the kicker too.
3) After every use I do the following once I get home. Rinse with a product called Salt Away and then wash the boat with soap and water. I might be able to get by with just the Salt Away rinse but am afraid to take a chance.
4) Wax, Wax Wax - I do this about once per month.

So far this seems to be working. I go thru this ritual as I intend this to be my last boat and have seen 1st hand the damage electrolisis / corrosion can cause.

Forgive me if this is a really stupid question, but does it matter if the zincs are below the waterline? Can I mount them up on the transom near the top? Or maybe inside the bilge?

when your boat is sitting in the water not running they should be in the water, when you mount them make sure you clean the surface your mounting them to real good and use stainless nuts and bolts.

i also agree with MJ!, the only difrence is i use lake washington